Instruction Manual

Chapter 5 Configuring the EM720
General Meter Setup
72 EM720 Power Quality and Revenue Meter
volts, and THD < 10% for currents. In networks with
high harmonics, the following method is preferable.
3. When the non-active power calculation mode is
selected, active power is measured directly, apparent
power is taken as product S = V x I, where V and I are
the RMS volts and amps, and reactive power (called
non-active power) is calculated as:
22
PSN −=
Tariff Control
The EM720 provides three options for switching tariff rates:
• automatic via a programmable TOU calendar schedule
(see Configuring the Daily Tariff Schedule
for
information on configuring tariff change points)
• external via communications by writing a tariff number
to the meter tariff register (see the EM720 Modbus
Reference Guide for information on the active tariff
register location)
• external via digital inputs by providing a tariff code on
the meter tariff inputs
If a digital input option is selected, you can use 1 to 3
consequent digital inputs as tariff inputs. The following table
shows the number of inputs required depending on the
maximum number of used tariff rates.
Number of tariffs Number of tariff inputs
2 1
3 2
4 2
5 3
6 3
7 3
8 3
The following table shows code combinations that should be
provided on the tariff inputs to indicate an active tariff rate.
Tariff code Tariff rate
number
Tariff
input 1
Tariff
input 2
Tariff
input 3
1 Open Open Open
2 Closed Open Open
3 Open Closed Open
4 Closed Closed Open
5 Open Open Closed
6 Closed Open Closed
7 Open Closed Closed
8 Closed Closed Closed